Today, dependence upon drugs of addiction causes major health problems worldwide. For example, alcohol abuse and alcohol dependency can cause liver, pancreatic and kidney disease, heart disease, including dilated cardiomyopathy, polyneuropathy, internal bleeding, brain deterioration, alcohol poisoning, increased incidence of many types of cancer, insomnia, depression, anxiety, and even suicide. Heavy alcohol consumption by a pregnant mother can also lead to fetal alcohol syndrome, which is an incurable condition. Additionally, alcohol abuse and alcohol dependence are major contributing factors for head injuries, motor vehicle accidents, violence and assaults, and other neurological and other medical problems.
Addiction to nicotine is estimated by the National Institute on Drug Abuse to kill nearly 500,000 Americans every year. This total represents about 1 in 6 of all deaths in the U.S. caused by any means, and is more than the total of deaths caused by use of alcohol, cocaine, heroin, suicide, car accidents, fire and AIDS combined. Cigarette smoking is the most popular method of using nicotine, but here are smokeless tobacco products; for example, snuff, chewing tobacco.
Nicotine addiction is linked to disease states such as leukemia, cataracts, and pneumonia; and is the cause of about one-third of all cancer deaths, the foremost of which is lung cancer. In addition to cancer, cigarette smoking also causes lung diseases, such as bronchitis and emphysema, exacerbates asthma symptoms, and is the cause of chronic obstructive pulmonary diseases in general. It is also well known that cigarette smoking increases the risk of cardiovascular diseases, including stroke, heart attack, vascular disease, aneurysm, and the like.
Another major health problem is caused by cocaine abuse. Physical effects of cocaine use include constricted blood vessels, dilated pupils, and increased temperature, heart rate, and blood pressure. A user of cocaine can experience acute cardiovascular or cerebrovascular emergencies, such as a heart attack or stroke, potentially resulting in sudden death. Other complications associated with cocaine use include disturbances in heart rhythm, chest pain and respiratory failure, seizures and headaches, and gastrointestinal complications such as abdominal pain and nausea. Because cocaine has a tendency to decrease appetite, many chronic users can become malnourished. Repeated use of cocaine may lead to a state of increasing irritability, restlessness, and paranoia. This can result in a period of full-blown paranoid psychosis, in which the user loses touch with reality and experiences auditory hallucinations.
Moreover, it is well known that the concurrent abuse of nicotine, cocaine and alcohol is common. It has been found that the combination of cocaine and alcohol exerts more cardiovascular toxicity than either drug alone in humans.
Historically, treating chemical dependence largely involved attempts to persuade patients to voluntarily discontinue use of the substance(s) (behavioral therapy). However, cocaine, morphine, amphetamines, nicotine, alcohol, and other types of dopamine-producing agents are highly addictive substances, and dependence upon such drugs can be harder to break and significantly more damaging than dependence on most other addictive substances. In particular, alcohol, cocaine, and heroin dependence are typically seen to be chronic relapsing disorders. There has been some moderate success in providing effective treatments for tobacco addiction by the use of nicotine replacement therapy, such as nicotine gum or the nicotine transdermal patch. Additionally, antidepressants and antihypertensive drugs have been tried, with modest success. Attempts have also been made to treat tobacco addiction by persuading patients to discontinue the use of tobacco voluntarily (behavioral therapy), but this method has not proved to be very successful. Accordingly, it is clearly desirable to find a treatment for tobacco addiction that reduces or prevents the craving for nicotine and does not involve nicotine replacement therapy or the use of antidepressants and antihypertensive drugs.
Accordingly, there has been much interest in the scientific community in attempting to find substances that could be employed to ameliorate dependency on addictive agents. Two compounds that have previously been employed for the treatment of alcohol abuse are known as disulfiram (Antabuse™) and cyanamide. Additionally, it has been recently proposed that disulfiram can be used for the treatment of cocaine dependency (for example, see Bonet et al., Journal of Substance Abuse Treatment, 26 (2004), 225-232).
More recently it has been shown that a compound known as daidzein is effective in suppressing ethanol intake. Daidzein is the major active component obtained from extracts of Radix puerariae, a traditional Chinese medication that suppresses ethanol intake in Syrian golden hamsters. See Keung, W. M. and Vallee, B. L. (1993) Proc. Natl. Acad. Sci. USA 90, 10008-10012 and Keung, W. M., Klyosov, A. A., and Vallee, B. L. (1997) Proc. Natl. Acad. Sci. USA 94, 1675-1679, and U.S. Pat. Nos. 5,624,910 and 6,121,010.
It has been shown that daidzin is an isoflavone of the formula:

Removal of the sugar provides a compound known as daidzein, which has also been shown to be effective in suppressing ethanol uptake.

U.S. Pat. Nos. 5,624,910 and 6,121,010 disclosed ether derivatives of daidzin, which were shown to be effective in treating ethanol dependency. Daidzin and its analogs were shown to be potent and selective inhibitors of human mitochondrial aldehyde dehydrogenase (ALDH-2), which is an enzyme involved in the major enzymatic pathway responsible for ethanol metabolism in humans. It was also found that daidzin analogues that inhibit ALDH-2 but also inhibit the monoamine oxidase (MOA) pathway were the least effective antidipsotropic activity.
In U.S. Patent Application Ser. No. 60/834,083, novel isoflavone derivatives were disclosed that are ALDH-2 inhibitors with little effect on the MOA pathway, and are useful for the treatment of alcohol dependency. It has now surprisingly been found that ALDH-2 inhibitors are also useful for the treatment of other addictive agents such as cocaine, heroin, and nicotine, and in particular, ameliorate the tendency of abusers to relapse.